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Subject: "Help with focus question" Previous topic | Next topic
lautry Silver Member Nikonian since 02nd Oct 2011Sat 06-Oct-12 08:49 PM
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"Help with focus question"


Panama City Beach, US
          

Hello Nikonians,
I am trying to take a series of dental pictures and I am trying different setups in an effort to "lock in" an acceptable zoom, f stop and shutter speed. The models will be on the same set up in a light box. I am trying to get the entire model in focus. I am using a tripod approx 18" from the subject. I started at an f stop of 5.6 at 150mm zoom, found the focal plane unacceptable and have increased to f18 to try and get a larger area of acceptable focus. I am locking focus on the teeth in the center of the model but i can still see the far edges drifting out of focus. I had to increase the iso to 1000 to get at least a 1/20 shutter speed. My question is am I going about this the easiest way? If i increase to f22 i will have to increase the iso or try to get some more light in the box. My only lens is 18-200mm. You folks are good and have helped this beginner many times. Thanks in advance.
Larry


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Attachment #1, (jpg file)

  

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Replies to this topic
Subject Author Message Date ID
Reply message RE: Help with focus question
RLDubbya Silver Member
07th Oct 2012
1
Reply message RE: Help with focus question
lautry Silver Member
07th Oct 2012
5
Reply message RE: Help with focus question
JosephK Silver Member
07th Oct 2012
2
Reply message RE: Help with focus question
lautry Silver Member
07th Oct 2012
6
Reply message RE: Help with focus question
km6xz Moderator
07th Oct 2012
3
Reply message RE: Help with focus question
lautry Silver Member
07th Oct 2012
4
     Reply message RE: Help with focus question
gkaiseril Gold Member
07th Oct 2012
7
          Reply message RE: Help with focus question
lautry Silver Member
07th Oct 2012
8

RLDubbya Silver Member Nikonian since 24th Dec 2011Sun 07-Oct-12 01:20 AM
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#1. "RE: Help with focus question"
In response to Reply # 0


US
          

IMO, a flash would be the easiest way to deal with this lighting challenge. Have you considered using one?

  

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lautry Silver Member Nikonian since 02nd Oct 2011Sun 07-Oct-12 12:31 PM
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#5. "RE: Help with focus question"
In response to Reply # 1


Panama City Beach, US
          

Thanks for the reply. I had not considered a flash because i was primarily concerned with focus and i shoot raw and can deal with the lighting in PP, but it can possibly be useful because of shadow enhancement of edge detail.
Thanks

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JosephK Silver Member Fellow Ribbon awarded for his excellent and frequent contributions and sharing his in-depth knowledge and experience with the community in the Nikonians spirit. Nikonian since 17th Apr 2006Sun 07-Oct-12 02:21 AM
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#2. "RE: Help with focus question"
In response to Reply # 0


Seattle, WA, US
          

In general, the DOF is split 50-50 from where you focus. Since you want both the front and back edges in focus, you need to set the focus point about half way into the model (as a starting point for testing). A line on the top of the model would help you in that point.

Since you are using a tripod, the slowness of the shutter speed should not matter, so there should be no real need to increase the ISO thus reducing any digital noise.

---------+---------+---------+---------+
Joseph K
Seattle, WA, USA

D700, D200, D70S, 24-70mm f/2.8, VR 70-200mm f/2.8 II, 50mm f/1.4 D,
17-55mm f/2.8 DX, 70-300mm f/4.5-5.6 VR, 18-70mm f/3.5-4.5 DX

  

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lautry Silver Member Nikonian since 02nd Oct 2011Sun 07-Oct-12 12:38 PM
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#6. "RE: Help with focus question"
In response to Reply # 2


Panama City Beach, US
          

I think you are right on about striking a focus a little deeper into the model but this is tricky because the DOF calculator would indicate i only have about a quarter of an inch to play with each way front and back. I have toyed around with distance and aperture and just can't seem to achieve a larger DOF with my lens and the requirements of this project.
I am a beginner and I seem to be given projects that are never easy.
Thanks so much for your help.
Larry

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km6xz Moderator Awarded for his in-depth knowledge in various areas, including Portraits and Urban Photography Nikonian since 22nd Jan 2009Sun 07-Oct-12 05:42 AM
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#3. "RE: Help with focus question"
In response to Reply # 0
Sun 07-Oct-12 05:50 AM by km6xz

St Petersburg, RU
          

Since you are focusing on the forward(plane closest to the camera) it would be natural to have the rear most area less in focus.
Using the tripod allows using Live View and manual focus but another way is to recreate a flag, a focus target placed on the top surface that aligned with the centermost plane you you seek. Anything that is a good focus target with contrast would work, a match box for example stood on the top to use as a focus target, on the desired FP. When focused, remove the matchbox and shoot. That way the front and rear depth of field will be balanced on either forward or backwards from that target. This should either be in VF manual or LV. You can also AF by half pressing the shutter to start focus and then press the AE/AF L button to lock that focus and exposure and shoot.
F22 is too small an aperture to prevent diffusion with the 16mpx of the D7000 so that should be opened up a little. Use the lowest ISO you can get the exposure since you are on tripod and in manual exposure mode.
What lighting source are you using outside of the light box? Continuous? If you lower the power of one of the light or move it slightly further away, subject detail can be increased. Edges are not well defined now because there are not enough shadows. Edge detail is low because the subject is of such a limited color and edges are soft. The lightbox is used to remove shadows from small objects that have a great deal of fine detail(along with other uses). In this case you actually need to emphasis edges more. Instead of a softbox, I probably would have used a multiple flash configuration to define edges more.

--Stan
St Petersburg Russia

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lautry Silver Member Nikonian since 02nd Oct 2011Sun 07-Oct-12 12:28 PM
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#4. "RE: Help with focus question"
In response to Reply # 3


Panama City Beach, US
          

Good advice. The target focus object was my next step. A DOF calculator would indicate about the best DOF i can muster given my current setup is about a quarter of an inch.Experimenting with the light source to greater define edges that are not too well defined is a good idea. I'm not too concerned about the lighting as I shoot raw and can fix most anything except focus in Lightroom/Photoshop.
The 18-200 is the only lens I have right now. If I do more of this work I wonder what lens would do a better job?
I use a single point focus and lock focus with the back button.
Thanks
Larry

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gkaiseril Gold Member Nikonian since 28th Oct 2005Sun 07-Oct-12 03:23 PM
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#7. "RE: Help with focus question"
In response to Reply # 4


Chicago, US
          

Zoom lenses are a compromise in design. I would look at using a prime lens designed for Macro use. You can rent Nikon and other lenses to test which lens would best meet your needs.

You should also look at for an online calculator, chart creators, and articles about DOF. The calculator will indicate the focus point distance, front and rear acceptable focus distances.

George
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lautry Silver Member Nikonian since 02nd Oct 2011Sun 07-Oct-12 03:45 PM
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#8. "RE: Help with focus question"
In response to Reply # 7


Panama City Beach, US
          

I seem to have resolved the focus issue by using the target concept, but achieving a similar result by moving my focus box from the closest point on the model to a tooth about halfway into the model depth, locking focus on that area and taking the shot via timer.
I do have a link to an online DOF calculator and that was where I learned I have an uphill battle given my challenge and my lens. There is not a lot of adjustment leeway and I have probably done the best I can do.
Thanks
Larry

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